Processing device using shower head structure and processing method

ABSTRACT

A processing device, comprising a processing container, a shower head structure provided at the ceiling part of the processing container and having a plurality of gas jetting holes for jetting specified processing gas into the processing container formed in the gas jetting surface thereof facing the inside of the processing container, and a placing stand disposed in the processing container so as to face the shower head structure, wherein a head distance between the gas jetting surface and the placing stand and the blowing speed of gas from the gas jetting holes are set within the range surrounded by connecting, in a square shape with straight lines in a plane coordinate system having the head distance plotted on an abscissa and the gas jetting speed plotted on a coordinate, a point where the blowing speed of the gas from the gas jetting holes at the head distance of 15 mm is 32 m/sec, a point where the blowing speed of the gas from the gas jetting holes at the head distance of 15 mm is 67 m/sec, a point where the blowing speed of the gas from the gas jetting holes at the head distance of 77 mm is 40 m/sec, and a point where the blowing speed of the gas from the gas jetting holes at the head distance of 77 mm is 113 m/sec.

FIELD OF THE INVENTION

The present invention relates to a processing apparatus and a processingmethod for processing an object to be processed such as a semiconductorwafer.

BACKGROUND OF THE INVENTION

In the course of manufacturing a semiconductor integrated circuit (IC),various single wafer processes such as a film forming process, anetching process, a heat treating process, a reforming process and acrystallization process are repeatedly carried out on an object to beprocessed, e.g., a semiconductor wafer. While executing such processes,processing gases needed for the corresponding processes, e.g., a filmformation gas for the film forming process; ozone gas or the like forthe reforming process; O₂ gas, an inert gas such as N₂ gas, or the likefor the crystallization process, are respectively introduced intoprocessing chambers.

For instance, in a single wafer processing apparatus for one by one heattreatment on semiconductor wafers, a mounting table incorporatingtherein, e.g., a resistance heater is installed in a processing chamberwhich can be evacuated. A processing gas is then introduced into theprocessing chamber after mounting a semiconductor wafer on the mountingtable to apply various heat treatments on the wafer under given processconditions.

In performing the various heat treatments, it is required to enhance thewithin wafer uniformity of each heat treatment and improve thethroughput thereof in order to maintain high productivity and at thesame time to improve electrical characteristics of manufacturedproducts.

In case of, for example, a reforming process for a tantalum oxide(Ta₂O₅) film used in a capacitor, ozone is introduced into a processingchamber which can be evacuated and the tantalum oxide film on thesurface of the wafer is annealed to be reformed under the presence of O₃(ozone). By such a reforming process, a carbonic component in thetantalum oxide film is removed in the form of CO₂. Accordingly,formation of a SiO₂ film at an interface between a polysilicon of anunderlying layer and the tantalum oxide film is facilitated, therebyimproving electrical characteristics. Further, a wafer temperature andan ozone concentration are raised sufficiently enough to improve anefficiency of the reforming process.

As the competition in the manufacturing field of semiconductor ICsbecomes ever fiercer recently, continuous improvement of theproductivity thereof has become one of the most important keys to remainsuccessful and profitable in the field. In the reforming processdescribed above, however, there is an upper limit in the wafertemperature set due to heat resistance of each layer of the underlyinglayers formed in preceding processes. The upper limit of the wafertemperature varies depending on a type of a film of the underlyinglayers and is for example about 720° C. Therefore, the wafer temperaturecannot be increased indefinitely in the reforming process for the sakeof improving the throughput.

Further, it may be attempted to increase an ozone concentration in orderto increase the throughput. Since, however, an ozone concentration islimited by an ozone generator, it is difficult to increase the ozoneconcentration beyond a current level.

SUMMARY OF THE INVENTION

The present invention is developed to solve such problems as describedabove. It is, therefore, an object of the present invention to provide aprocessing apparatus and a processing method capable of improvingthroughput of heat treatment by maintaining within wafer uniformity ofthe heat treatment high.

From a study on a reforming process by annealing performed under thepresence of ozone, the inventors reached a conclusion that an efficiencyof the reforming processing can be increased by setting a gas jettingvelocity of a processing gas from a shower head structure into aprocessing chamber at a high rate within a specific range.

In accordance with the present invention, there is provided a processingdevice, including: a processing chamber; a shower head structure,installed at a ceiling portion of the processing chamber, having aplurality of gas jetting holes formed on a gas jetting surface to injecta processing gas into the processing chamber, the gas jetting surfacefacing toward an inside of the processing chamber; and a mounting tableinstalled in the processing chamber to face toward the shower headstructure, wherein a head distance between the gas jetting surface andthe mounting table (conventionally, defined irrespective of a thicknessof an object to be processed) and a gas jetting velocity from the gasjetting holes are restricted to be within an area in a plane coordinatessystem having the head distance as a horizontal axis and the gas jettingvelocity as a vertical axis, the area being surrounded by aquadrilateral shape formed by connecting four points including a pointwhere the gas jetting velocity is 32 m/sec and the head distance is 15mm; a point where the gas jetting velocity is 67 m/sec and the headdistance is 15 mm; a point where the gas jetting velocity is 40 m/secand the head distance is 77 mm; and a point where the gas jettingvelocity is 113 m/sec and the head distance is 77 mm.

In accordance with the present invention, if a gas jetting velocity fromgas jetting holes of the shower head structure is set such that a headdistance between the shower head structure and the mounting table iswithin an optimal range, a throughput can be increased by improving aprocessing efficiency while maintaining a high level of within waferuniformity of a processing.

For example, the gas jetting holes of the gas jetting surface is formedin a forming area of a circular shape and an object to be processedloaded on the mounting table is also formed of a circular shape.

In this case, a diameter of the forming area of the gas jetting holes inthe gas jetting surface is preferably set to be equal to or smaller thana diameter of the object to be processed to thereby further enhance thelevel of the within wafer uniformity of a processing.

In particular, the diameter of the forming area of the gas jetting holesin the gas jetting surface is preferably 70% to 100% of the diameter ofthe object to be processed.

Preferably, the processing gas contains ozone for reforming a metaloxide film formed on a surface of the to-be-processed object.

Moreover, preferably, the metal oxide film is a tantalum oxide film.

Further, in accordance with another aspect of the present invention,there is provided a processing method for processing an object to beprocessed by using a processing apparatus including a processingchamber; a shower head structure, installed at a ceiling portion of theprocessing chamber, having a plurality of gas jetting holes formed on agas jetting surface thereof to inject a processing gas into theprocessing chamber, the gas jetting surface facing toward an inside ofthe processing chamber; and a mounting table installed in the processingchamber to face toward the shower head structure, the method includingthe steps of: restricting a head distance between the gas jettingsurface and the mounting table and a gas jetting velocity from the gasjetting holes to be within an area in a plane coordinates system havingthe head distance as a horizontal axis and the gas jetting velocity as avertical axis, the area being surrounded by a quadrilateral shape formedby connecting four points including a point where the gas jettingvelocity is 32 m/sec and the head distance is 15 mm; a point where thegas jetting velocity is 67 m/sec and the head distance is 15 mm; a pointwhere the gas jetting velocity is 40 m/sec and the head distance is 77mm; and a point where the gas jetting velocity is 113 m/sec and the headdistance is 77 mm; loading the object to be processed on the mountingtable; and introducing the processing gas through the gas jetting holesinto the processing chamber.

Preferably, the processing gas contains ozone for reforming a metaloxide film formed on a surface of the object to be processed.

Further, preferably, the metal oxide film is a tantalum oxide film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a processing apparatus in accordancewith a preferred embodiment of the present invention;

FIG. 2 provides a bottom view of a shower head structure shown in FIG.1;

FIG. 3 explains an optimum range relationship between a gas jettingvelocity and a head distance;

FIG. 4 sets forth a graph for describing a relationship between a gasjetting velocity when performing a reforming process by annealing and athickness of a SiO₂ film (processed for 5 minutes) formed during theprocess;

FIG. 5 depicts a graph showing a relationship between an O₃concentration and a SiO₂ film thickness;

FIG. 6 provides a graph for describing an upper limit of a gas jettingvelocity in case a head distance is 77 mm;

FIG. 7A provides a simulation result of a gas jetting velocitydistribution of gas, which is injected from a shower head structure of aconventional processing apparatus, in a processing space and FIG. 7Bshows a simulation result of a gas jetting velocity distribution of gas,which is injected from the shower head structure of the processingapparatus of the present invention, in a processing space;

FIG. 8 is a graph describing a relationship between a gas jettingvelocity and a thickness of a SiO₂ film (processed for 5 minutes); and

FIG. 9 explains an upper limit of a gas jetting velocity in case a headdistance is about 15 mm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a processing apparatus and a processing method inaccordance with a preferred embodiment of the present invention will bedescribed with reference to the accompanying drawings.

FIG. 1 shows a cross sectional view of the processing apparatus inaccordance with the preferred embodiment of the present invention. FIG.2 provides a bottom view of a shower head structure shown in FIG. 1.FIG. 3 presents a graph for describing an optimal range of a gas jettingvelocity as a function of a head distance. The processing apparatus ofthis preferred embodiment is the one for reforming tantalum oxide filmsthrough an annealing process.

As shown in FIG. 1, a processing apparatus 2 has a processing chamber 4made of aluminum and an inside of the processing chamber 4 isapproximately of a cylindrical shape. Installed on a ceiling portion ofthe processing chamber 4 is a shower head structure 6 functioning as agas supply unit for introducing a required processing gas, e.g., amixture gas of O₂ and O₃, or a mixture gas thereof further having activespecies of oxygen *O. A gas jetting surface 8 of a bottom surface of theshower head structure 6 has a plurality of gas jetting holes 10, so thatthe processing gas is injected through the plurality of gas jettingholes 10 toward a processing space S.

A gas diffusion room 12 of a hollow shape is formed inside the showerhead structure 6. The processing gas is horizontally diffused in the gasdiffusion room 12 and then injected through each of the gas jettingholes 10. The entire shower head structure 6 is formed of, e.g., nickel,a nickel alloy of Hastelloy (registered trademark) or the like, aluminumor an aluminum alloy. A ring-shaped guide protrusion 14 projectingdownward is formed along a periphery of the gas jetting surface 8 of theshower head structure 6 in order to guide a downward flow of theprocessing gas. In addition, a sealing member 16 made of, e.g., anO-ring is provided at an abutment of the shower head structure 6 and anopen top of the processing chamber 4, thereby helping to maintain theinside of the processing chamber 4 airtight.

Formed on a sidewall 4A of the processing chamber 4 is a gate 18 throughwhich an object processed or to be processed, i.e., a semiconductorwafer W, is carried into and out of the processing chamber 4. Installedat the gate 18 is a gate valve 20 capable of being airtightly opened andclosed.

Further, an exhaust gas downdraft space 24 is formed at a bottom portion22 of the processing chamber 4. Specifically, a large entrance opening26 is provided at a central portion of the bottom portion 22 of theprocessing chamber 4 and the entrance opening 26 is connected to adownwardly extending cylindrical enclosure wall 28 of a cylindricalshape having a bottom surface, which includes therein the exhaust gasdowndraft space 24. A support 30 of, e.g., a cylindrical shape stands ona bottom portion 28A of the cylindrical enclosure wall 28 enclosing theexhaust gas downdraft space 24. A mounting table 32 is fixed on top ofthe support 30.

A diameter of the entrance opening 26 of the exhaust gas downdraft space24 is set to be smaller than that of the mounting table 32. Thus, aprocessing gas flowing downward along an outer region of the peripheryof the mounting table 32 curves inward under the mounting table 32 andthen flows into the entrance opening 26. Further, installed on an innerwall of the processing chamber 4 is a ring-shaped guide plate 34inwardly protruding toward a bottom area of the mounting table 32. Thus,atmosphere being exhausted is guided toward the entrance opening 26 bythe ring-shaped guide plate 34. An exhaust port 36 communicating withthe exhaust gas downdraft space 24 is formed on a bottom sidewall of thecylindrical enclosure wall 28. The exhaust port 36 is connected to anexhaust line 38 where a vacuum pump (not shown) is installed to therebymake it possible to exhaust the atmosphere of the processing chamber 4and the exhaust gas downdraft space 24.

A pressure control valve (not shown) whose opening can be controlled isinstalled on the exhaust line 38. By automatically controlling thedegree of opening of the pressure control valve, a pressure inside theprocessing chamber 4 can be maintained at a constant level or rapidlychanged into a desired pressure.

The mounting table 32 is provided with a heating device, e.g., aresistance heater 40 disposed in a predetermined pattern inside themounting table 32. An outer portion of the mounting table 32 is made ofa sintered ceramic composed of, e.g., AlN or the like. Further, asemiconductor wafer W, i.e., an object to be processed, can be loaded ona top surface of the mounting table 32. The resistance heater 40 isconnected to feeder lines 42 disposed inside the support 30. Therefore,it is possible to control power applied to the resistance heater 40.

The mounting table 32 is provided with a plurality of, e.g., three, pininsertion through holes 44 (only two are shown in FIG. 1) verticallyrunning therethrough. Inserted through each of the pin insertion throughholes 44 is a vertically movable upthrust pin 46. A bottom portion ofthe upthrust pin 46 is connected to an upthrust ring 48 made of ceramicsuch as alumina and formed in an arc shape obtained by partially cuttinga circular ring. That is, a top surface of the upthrust ring 48 supportsthe bottom of each upthrust pin 46. An arm unit 48A extending from theupthrust ring 48 is connected to an up/down rod 50 passing through thebottom portion 22 of the processing chamber 4 and the up/down rod 50 isconfigured to be vertically moved by an actuator 52. Accordingly, whenloading and unloading the wafer W, each upthrust pin 46 is verticallymoved up or down from a top portion of each pin insertion through hole44. Further, an expansible/contractible bellows 54 is installed betweenthe actuator 52 and a portion of the bottom potion 22 of the processingchamber 4 through which the up/down rod 50 of the actuator 52 passes.Therefore, the up/down rod 50 can be vertically movable while keepingthe inside of the processing chamber 4 airtight.

The following is a detailed description of the shower head structure 6featuring the present invention. As illustrated in FIG. 2, in the showerhead structure 6, a plurality of gas jetting holes 10 are formed in anapproximately circular area in a substantially uniformly distributedfashion. An inner diameter of each of the gas jetting holes 10 rangesfrom, e.g., about 0.4 to 0.8 mm and the number of the gas jetting holes10 ranges from about 50 to 800. It has been found by the inventors ofthe present invention that a diameter D1 of a circular forming area 56in which the gas jetting holes 10 are formed is preferably smaller thanor equal to a diameter D2 (see FIG. 1) of the semiconductor wafer W.Preferably, the diameter D1 of the forming area 56 is set to be in arange from 70% to 100% of the diameter D2 of the wafer W.

When a head distance L1 in this embodiment is defined as a distancebetween the gas jetting surface 8 and a placing surface 32A of themounting table 32, there is a relationship between the head distance L1and a gas jetting velocity V1 from the gas jetting holes 10 that isrestricted to hold in a shaded area as shown in a graph of FIG. 3, i.e.,the area being encompassed by a quadrilateral formed by connecting thefollowing four points by straight lines: a point where the head distanceL1 and the gas jetting velocity V1 are 15 mm and 32 m/sec, respectively;a point, 15 mm and 67 m/sec; a point, 77 mm and 40/sec; and a point, 77mm and 113 m/sec.

By restricting the relationship between the head distance L1 and the gasjetting velocity V1 to hold within the shaded area shown in FIG. 3, asurface velocity of gas flow on a wafer surface can be optimized tothereby maintain a high level of within wafer uniformity of a processingand improve the processing efficiency and throughput, as will bedescribed later.

Hereinafter, an operation of the processing apparatus having theaforementioned structure will be described.

Before the semiconductor wafer W is loaded into the processing chamber4, an inner space of the processing chamber 4 of the processingapparatus 2 connected to a load lock chamber (not shown) is, e.g.,evacuated. Further, the mounting table 32 for loading thereon the waferW is heated by the resistance heater 40 acting as a heating device up toa predetermined temperature, which is then stably maintained at thetemperature.

Next, the semiconductor wafer W to be processed is loaded into theprocessing chamber 4 by a transfer arm (not shown) through the gatevalve 20 that is opened and the gate 18. The wafer W is placed on theupthrust pin 46 that has been lifted. Then, the upthrust pin 46 movesdownward, so that the wafer W can be loaded and supported on a topsurface of the mounting table 32. A surface of the wafer W made of asilicon substrate of this preferred embodiment is coated with a metaloxide film, e.g., a tantalum oxide film, formed in a preceding process.

Thereafter, a processing gas including, e.g., O₂ and O₃ is supplied tothe shower head structure 6 at a controlled flow rate. The gas isspurted (jetted) from the gas jetting holes 10 to be introduced into theprocessing space S. Further, a vacuum pump (not shown) provided at theexhaust line 38 is kept operating continuously to maintain the vacuumstate in the processing chamber 4 and the exhaust gas downdraft space24. Moreover, by controlling an opening degree of the pressure controlvalve, the atmosphere of the processing space S can be maintained at apredetermined operating process pressure. At this time, a temperature ofthe wafer W is maintained at, e.g., about 660° C., and, therefore, thetantalum oxide film on the surface of the semiconductor wafer W isannealed to be reformed by O₂, O₃, or the like.

As described above, the relationship between the head distance L1 andthe gas jetting velocity V1 from the gas jetting holes 10 is restrictedto hold within a shaded area as shown in a graph of FIG. 3, i.e., thearea encompassed by a quadrilateral formed by connecting the followingpoints by straight lines: a point P1 where the head distance L1 and thegas jetting velocity V1 are 15 mm and 32 m/sec, respectively; a pointP2, 15 mm and 67 m/sec; a point P3, 77 mm and 40/sec; and a point P4, 77mm and 113 m/sec.

By restricting the relationship between the head distance L1 and the gasjetting velocity V1 to hold within the shaded area shown in FIG. 3, asurface velocity of gas flow on the wafer surface can be optimized tothereby maintain a high level of within wafer processing uniformity andimprove processing efficiency and throughput.

The following is a detailed description thereof.

FIG. 4 presents a graph showing a relationship between a gas jettingvelocity and the SiO₂ film thickness when a semiconductor wafer made ofa silicon substrate having a diameter of 200 mm was annealed to performa reforming processing. FIG. 5 represents a graph illustrating arelationship between an O₃ concentration and the SiO₂ film thickness.FIG. 6 provides a graph for explaining a maximum value of the gasjetting velocity in case the head distance is 77 mm.

As illustrated in FIG. 4, a relationship between the gas jettingvelocity V1 from the gas jetting holes 10 of the shower head structure 6and the SiO₂ film thickness was examined in order to evaluate areforming performance. The size of the used wafer was 200 mm and thehead distance L1 was 77 mm. Further, a process temperature and a processpressure were about 660° C. and about 30 Torr (4000 Pa), respectively.In curves A and B of FIG. 4, a flow rate of O₂ gas was constant at 10000sccm, and 1.30% of a total flow rate was replaced with an O₃ gas.Moreover, an N₂ gas was added within the range of 0 to 7000 sccm inorder to change the jetting velocity. In addition, in a curve C of FIG.4, a flow rate Of O₂ gas varied from 7000 to 10000 sccm, and 1.30% of atotal flow rate was replaced with an O₃ gas. However, an N₂ gas was notadded.

Herein, the reforming performance is evaluated based on a thickness of aSiO₂ film (film forming rate) since the film forming rate of the SiO₂film increases as the reforming performance is improved and therefore,in a reforming processing performed for an equal processing time, it canbe determined that a thicker SiO₂ film represents an improved reformingperformance.

In order to vary the gas jetting velocity V1, a flow rate of O₂ or N₂gas was changed. In this case, an O₃ concentration as well as the gasjetting velocity V1 is also changed. However, as illustrated in FIG. 5,since a relationship between the SiO₂ film thickness and the O₃concentration is substantially flat at least within a range of theconcentration of O₃ used in this preferred embodiment, it can be seenthat the dependency of O₃ concentration on the SiO₂ film thickness isvery small. Therefore, a variation in the film forming rate of the SiO₂film shown in FIG. 4 can be regarded as being dependent on the gasjetting velocity V1, as will be explained below. In FIG. 5, the O₃concentration varies within the range from 0.5 to 2.5%.

The gas jetting velocity V1 is represented by a following equation.V1=Q·(273+T)/(K·A·P·273)

Q: a gas flow rate (sccm)

A: a total area (m²) of all the gas jetting holes of the shower head

P: a pressure (Pa) at the gas jetting holes of the shower head

T: a temperature (° C.) of the shower head

K: a conversion constant=592

In case of data plotted on the curve A of FIG. 4, an inner diameter andthe number of the gas jetting holes 10 were 0.8 mm and 368,respectively. These data corresponds to a conventional shower headstructure. Especially, a conventional reforming annealing process isperformed under the condition represented by a leftmost point Al amongthe data on the curve A.

In case of data plotted on the curve B, an inner diameter and the numberof the gas jetting holes 10 were 0.8 mm and 140, respectively. In caseof data plotted on the curve C, an inner diameter and the number of thegas jetting holes 10 were 0.8 mm and 88, respectively. The shower headstructures whose respective numbers of the gas jetting holes 10 are 140and 88 can be respectively obtained by sealing the gas jetting holes 10within a certain distance from the outermost peripheral region in theconventional shower head structure.

As can be clearly seen from the graph of FIG. 4, an increase in the gasjetting velocity V1 generally raises the thickness of the SiO₂ film(film forming rate) formed by the reforming processing.

In the conventional shower head structure corresponding to the curve A,a film thickness at point A1 was about 20 Å. Until the gas jettingvelocity V1 reaches to about 40 m/sec, the film thickness increases asthe gas jetting velocity increases. However, even if the gas jettingvelocity V1 is increased further, the film thickness is saturated atabout 23 Å and there is no further increase.

On the contrary, when the gas jetting velocity V1 was increased to ahigher level corresponding to the curves B or C by reducing the numberof gas jetting holes 10, the SiO₂ film thickness was increased to reachabout 24 to 25 Å when the gas jetting velocity was in the range between70 and 113 m/sec, so that a higher film forming rate could be achieved.Considering an upper limit of film forming rate during five minutes is20 Å at a point A1 corresponding to a conventional gas jetting velocityin a conventional case where the number of the gas jetting holes 10 is368, a new and preferable lower limit of the gas jetting velocity V1 isdetermined to be about 40 m/sec corresponding to the SiO₂ film thicknessof 23 Å. More preferably, the lower limit of the gas jetting velocity V1is about 70 m/sec corresponding to the film forming rate of 24 Å duringfive minutes, which cannot be achieved in the conventional shower headstructure.

Next, an upper limit of the gas jetting velocity V1 was examined.

As shown in FIG. 6, the SiO₂ film thicknesses in a radial direction of awafer were investigated in case the gas jetting velocities V1 were 113m/sec (corresponding to a point C1 of FIG. 4) and 207 m/sec,respectively. Other processing conditions were same as those explainedwith reference to FIG. 4.

As illustrated in FIG. 6, in case the gas jetting velocity was 113m/sec, irregularities in the film thickness were not so serious and thewithin wafer uniformity thereof showed a satisfactory result of 3.82%.On the other hand, in case of an excessively high gas jetting velocityof 207 m/sec, film thicknesses in regions corresponding to the gasjetting holes 10 became extremely thin (because pattern of the gasjetting holes were printed [transferred]), thereby generating largeoverall irregularities.

Thus, in case the gas jetting velocity was 207 m/sec, the uniformity inthe film thickness was deteriorated down to 15.63%, resulting inproducing an unsatisfactory film. The reason why the film forming rateis increased as the gas jetting velocity V1 is increased is presumedthat the increase in the gas jetting velocity V1 results in an increasein a surface velocity of gas on the wafer surface, which in turn causesan oxidizing power of O₂ gas and O₃ gas for tantalum oxide film to beaugmented.

Resultantly, in case the head distance L1 is 77 m, an upper and a lowlimit of a new and preferable gas jetting velocity V1 are considered tobe 113 m/sec and 40 m/sec, respectively.

Further, as shown in FIG. 4, the within wafer uniformity of filmthickness under conditions corresponding to the curve A was about 9.86to 14.98%, which is not so good; but those under the conditionscorresponding to the curves B and C were very good, falling in the rangefrom about 3.32 to 3.82%.

Furthermore, the forming area 56 (see FIGS. 1 and 2) on which 140 (curveB) or 88 (curve C) gas jetting holes 10 are provided has a diameter D1,which is smaller than or equal to a diameter D2 of the wafer W. Forexample, the diameter D1 is set to range from about 70% to 100% of thediameter D2. Resultantly, the within wafer uniformity of film thicknessis further more improved. In case the number of the gas jetting holes 10is 386 (curve A), the diameter D1 of the forming area 56 was set to beslightly larger than the diameter D2 of the wafer W.

A distribution of gas flow velocities in the processing space wassimulated for each of two cases where a shower head structure of aconventional processing apparatus and a shower head structure of theprocessing apparatus of the present invention are employed to inject agas. The simulation result is as follows.

FIGS. 7A and 7B are graphs, each representing the simulation result of aright half portion within a processing chamber. FIG. 7A illustrates aflow velocity distribution of a gas injected from the shower headstructure of the conventional processing apparatus, which corresponds tothe curve A in FIG. 4. FIG. 7B shows a flow velocity distribution of agas injected from the shower head structure of the present invention,which corresponds to the curves B or C in FIG. 4. In the drawings, awhiter portion represents a region of a higher gas jetting velocity.

In case of the conventional processing apparatus, as shown in FIG. 7A, agas flow velocity is not so high on the surface of the wafer W and islarge only at a peripheral portion of the wafer W. On the other hand,the processing apparatus of the present invention has a high gas flowvelocity on almost entire surface region of the wafer W, as shown inFIG. 7B.

The processing apparatus of the present invention described above wasthe one applicable to a wafer having a size of 200 mm and had a headdistance L1 of about 77 mm. However, the wafer size is not limited to200 mm. For example, the present invention can be applied to aprocessing apparatus for treating a wafer of a size of 300 mm. In caseof the processing apparatus for a wafer of a size of 300 mm, a diameterof each of the mounting table 32 and the shower head structure 6 isincreased to match the increase in the wafer size. However, the headdistance L1 can be conversely set to be smaller, for example, about 15mm, to cope with a demand for a size reduction of a processingapparatus.

The same experiment as described above was conducted for the processingapparatus for the wafer of 300 mm in case a head distance L1 was 15 mm.As a result, it was found that a new and a preferable upper limit of thegas jetting velocity V1 was about 67 m/sec, i.e., lower than the upperlimit of 113 m/sec in the processing apparatus for treating the waferhaving a size of 200 mm. It is presumed that a reduction in the headdistance L1 from 77 mm to 15 mm facilitates the print (transfer).Further, the lower limit of the gas jetting velocity in this case wasfound to be about 32 m/sec, when a minimum value of a film forming ratefor a time period of 5 minutes is about 23 Å, preferably about 40 m/sec.

In this case, the number of the gas jetting holes 10 was 761 and theirdiameter was set to be 0.4 mm in order to maintain a high flow velocityand restrain the print while achieving a uniform flow thereof. Further,a process temperature and a process pressure were set to be respectively660° C. and 30 Torr (4000 Pa). A flow rate of O₂ gas was varied within arange from 6000 to 10000 sccm while a flow rate of N₂ gas was changedwithin a range from 0 to about 9000 sccm, in order to change the gasjetting velocity V1. Further, a gas flow rate of O₃ was changed within arange from 0.68% to 2.17% of the total flow rate.

FIG. 8 is a graph for describing a relationship between a gas jettingvelocity V1 and a thickness of a SiO₂ film (processed for 5 minutes). Asshown in FIG. 8, a film forming rate higher than the conventional filmforming rate of 20 Å (corresponding to point A1 in FIG. 4) was achievedover an entire range of gas jetting velocity from 32 m/sec to 102 m/sec.Further, a flow rate of O₂ gas needs to be set smaller than or equal to6000 sccm in a range of a gas jetting velocity V1 smaller than 32 m/sec.Since, however, an ozone generation from an ozone generator may not beperformed stably in case the flow rate of O₂ gas is reduced, data inthis range could not be obtained.

Further, FIG. 9 is a graph for describing an upper limit of gas jettingvelocity in case a head distance is 15 mm. As shown therein,irregularities in the film thickness was not so serious and the withinwafer uniformity of the film thickness showed a good result of 3.5% incase a gas jetting velocity V1 is 67 m/sec. In contrast, in case the gasjetting velocity V1 was 102 m/sec, there occurred a serious print,resulting in large irregularities and an unsatisfactory within waferuniformity of a film thickness of 7.2%. Therefore, the upper limit ofgas jetting velocity V1 can be regarded as 67 m/sec.

The lower limit of gas jetting velocity V1 is 32 m/sec at the maximum,though a smaller value is expected. Therefore, the shaded areasurrounded by a quadrilateral formed by connecting the points P1 to P4in FIG. 3 is a proper area. Further, if a processing apparatus having ahead distance smaller than 15 mm is developed by technologicalinnovation, the proper range of gas jetting velocity is expected to befurther extended to a left area in FIG. 3.

As described above, it was found that the shaded area surrounded by thequadrilateral formed by connecting the points P1, P2, P4 and P3 was anarea of optimum conditions for the reforming annealing processing.

By arbitrarily setting the head distance L1 and the gas jetting velocityV1 within the shaded area shown in FIG. 3, the within wafer processinguniformity can be maintained to be at a high level while improvingefficiency of the processing and throughput thereof.

Furthermore, diameters and the numbers of the gas jetting holes 10 inthe preferred embodiment are mere representation of examples and thusare not limited thereto.

Still further, though the processing apparatus for the reformingannealing process of a tantalum oxide film has been disclosed in thepreferred embodiment of the present invention, the present invention canbe applied to a thermal CVD processing apparatus, a plasma CVDprocessing apparatus, an etching processing apparatus, an oxidationdiffusion processing apparatus, a sputtering processing apparatus, andthe like.

Furthermore, though the preferred embodiment employs a semiconductorwafer as the object to be processed, the object to be processed is notlimited thereto and an LCD substrate, a glass substrate and the like,can be employed.

1. A processing method for processing an object to be processed by usinga processing apparatus including a processing chamber; a shower headstructure, installed at a ceiling portion of the processing chamber,having a plurality of gas jetting holes formed on a gas jetting surfacethereof to inject a processing gas into the processing chamber, the gasjetting surface facing toward an inside of the processing chamber; and amounting table installed in the processing chamber to face toward theshower head structure, the method comprising the steps of: loading theobject to be processed on the mounting table; and introducing theprocessing gas through the gas jetting holes into the processingchamber, wherein while processing the object, a head distance betweenthe gas jetting surface and the mounting table and a gas jettingvelocity from the gas jetting holes are restricted to be within an areain a plane coordinates system having the head distance as a horizontalaxis and the gas jetting velocity as a vertical axis, the area beingsurrounded by a quadrilateral shape formed by straight lines connectingfour points including a point where the gas jetting velocity is 32 m/secand the head distance is 15 mm; a point where the gas jetting velocityis 67 m/sec and the head distance is 15 mm; a point where the gasjetting velocity is 40 m/sec and the head distance is 77 mm; and a pointwhere the gas jetting velocity is 113 m/sec and the head distance is 77mm.
 2. The method of claim 1, wherein the processing gas contains ozonefor reforming a metal oxide film formed on a surface of the object to beprocessed.
 3. The method of claim 2, wherein the metal oxide film is atantalum oxide film.
 4. The method of claim 1, wherein while processingthe object, a pressure inside the processing chamber is maintained at aconstant level.
 5. The method of claim 1, wherein while processing theobject, a temperature of the object to be processed is maintained at aconstant level.
 6. A processing method for processing an object, saidmethod comprising: loading the object onto a mounting table providedwithin a processing chamber having a plurality of gas jetting holesformed on a gas jetting surface facing towards the mounting table; andinjecting a processing gas into the processing chamber through theplurality of gas jetting holes while restricting a distance between thegas jetting surface and the mounting table and a velocity of theprocessing gas from the plurality of gas jetting holes to be within anarea in a plane coordinates system having the distance as a first axisthereof and the velocity as a second axis that is perpendicular to thefirst axis, wherein the area has a quadrilateral shape formed by a firstline connecting a first point where the velocity is 32 m/sec and thedistance is 15 mm and a second point where the velocity is 67 m/sec andthe distance is 15 mm, a second line connecting the first point to athird point where the velocity is 40 m/sec and the distance is 77 mm, athird line connecting the second point to a fourth point where thevelocity is 113 m/sec and the distance is 77 mm, and a fourth lineconnecting the third point to the fourth point.
 7. The method of claim6, wherein the processing gas being injected into the processing chambercontains ozone for reforming a metal oxide film formed on a surface ofthe object.
 8. The method of claim 7, wherein the metal oxide film is atantalum oxide film.
 9. The method of claim 6, further comprisingmaintaining a pressure within the processing chamber at a constant levelwhile the processing gas is being injected into the processing chamber.10. The method of claim 6, further comprising maintaining a temperaturewithin the processing chamber at a constant level while the processinggas is being injected into the processing chamber.
 11. The method ofclaim 6, wherein the processing chamber in which the object is loaded isconfigured such that the plurality of gas jetting holes are all providedwithin a circular area on the gas jetting surface, and such that themounting table has a circular shape.
 12. The method of claim 11, whereinthe circular area has a diameter that is equal to or smaller than adiameter of the object.
 13. The method of claim 11, wherein the circulararea has a diameter that is 70% to 100% of a diameter of the object.